1. Field of the Invention
This invention relates to a truck for high speed rail vehicles, especially for high speed passenger rail cars, in which the dynamic stability of the wheel sets is assured up to speeds exceeding 124.3 miles per hour (200 kilometers per hour). The term "truck" as used herein refers to the part of the vehicle which contains one or more wheel sets, especially a swivel truck having two or more wheel sets. This invention is particularly directed to a truck in which the wheel sets are guided stiffly in the direction of travel by use of an elastic material having an elastic constant greater than 200 kiloponds per millimeter per axle bearing which is disposed directly on the car body or in a frame which is joined to the car body. The trucks of the invention are further characterized by having a resilient elastic layer disposed between the wheel crown of the wheel and the hub thereof.
2. Discussion of the Prior Art
It is known that high track speeds can be achieved if the pivoting movement of the wheel set or swivel truck, as the case may be, about its vertical axis, is retarded by a stabilizing means. It is also known that the effect of a stabilizing means can be improved if the wheel sets are so mounted in the swivel truck or on the car that movements of the wheel axle bearings in the direction of travel are opposed by great forces, i.e., the elastic constant in the direction of travel is great.
Running speeds of up to 200 km/h can be achieved if, in addition to the axle mounting which is very stiff in the direction of travel, a wheel profile having a shallow conical inclination is used. It has been found, however, that the wheel profile is changed by wear and ultimately assumes a shape that is virtually independent of the initial profile and ceases to be changed by further wear. This constant profile produced by wear, however, has a relatively great effective conical inclination, resulting in an instability of the operation of the wheel set above a certain critical speed. This so-called zigzagging produces very great lateral forces, so that the car can no longer be operated at maximum speeds with this profile due to wear.
To prevent this instability and enable cars to run at maximum speed, the wheel sets have had to be frequently turned or ground down in order to obtain the profile with the shallow conical inclination. The necessity of frequently turning or grinding down the wheel sets, however, is not acceptable in practical operation.
The stabilization of wheel set operation by torsional drag, which has been successful at speeds up to 200 km/h, is no longer sufficient at speeds above 200 km/h and with wheels of worn profile.
It has, therefore, become desirable to provide a truck for a high speed rail vehicle in which there is maximum dynamic stability when the truck moves at speeds exceeding 200 km/h. More especially, it has become desirable to provide a truck in which maximum stabilization of the wheel sets is provided without the so-called zigzagging which produces the great lateral forces in an apparatus which does not require the turning or grinding down of wheel sets. More especially, it has become desirable to provide a truck for a high speed rail vehicle which can be moved at speeds exceeding 124.3 mi/hr (200 km/h) and even at speeds up to 186.4 mi/hr (300 km/hr).